Yanmar L100 Clone Teardown

Hello fellas. So I kinda got the idea to teardown one of these 10hp air-cooled diesels a lot of people are running, and document it in a thread here. Just thought that it'd be handy for some folks to see just what makes these things tick and all, since I don't know if there's much online covering the internal workings.

Well anyways, here it is:



Nothing fancy, just a 10hp genset engine. I was told it had a cracked piston, which was no doubt caused by a nut entering the combustion chamber at some point, as told by the heavy witness marks on both the cylinder head and piston:





Yep, that's not good! A couple hairline cracks visible, you can also see the swirl crater and the recesses for the valves.

First thing I wanted to do was pull the side cover, which is no joke because they have 16 bolts holding the thing on:



So I went to drain the oil and when I popped the plug nothing came out. But if I pulled the dipstick black diesel oil came gushing out. Well I got most of the oil out, yanked the side cover and found out just maybe why it wasn't draining:







Oh yeah, LOL. That's good stuff right there! Sludge in the bottom that like had a gelatinous form and the oil was just sitting on top. Yuck, haha.

Well got that cleaned out to some degree, still needs some but it's better than before, haha.



It has a single counter-balancer driven by a gear on the flywheel side of the crank:



Timing marks on both gears to time the counter-balancer:



After that I pulled the rod and piston. The rod is cast iron with bearing inserts:



Then I saw the full extent of the damage to the piston:











Wow, hahaha. She's definitely had 'er last. It's gonna make a dang good wall hanger though!!

But anyway, that's all I got to for tonight. Next I'll probably go into the cam, valve train, injector pump, etc. Just figured I'd put as much info in here as possible.

More to come!

thats crazy, I have one of these kicking around supposed to have bad rings wonder if the piston is just cracked?

Haha, yep. Pretty wild!

Yeah you could be right about that, might be worth investigating.

Dang, that's not cracked, that's what you call shattered! Must of been one heck of a nut...

Well just think of the compression on a diesel though, that nut was in one seriously tight space!

Plans on rebuilding and running it?

That's crazy. Thanks for sharing

Maybe that'll work in my yanmar, wanna trade it for a lightly used K181 con rod? Lol.
Pretty crazy to see that.

Haha, yeah it's pretty crazy. The way everything else looks I imagine I could indeed install a new piston and rings and it's be good to go, but we'll see. I only bought it for parts though so I'm not too concerned.

Alrighty, got another minute to tinker with this the other day so I figured I'd go over the injector pump and lower valvetrain.

Here's the cam and injector pump:



Then the tappets and push rods, both of which are the same length.



The center lobe on the cam is what controls the injector pump timing, there's a little steel cup that goes on the end of the pump:



Closer look at the pump:



The the threaded fitting directly on top is for the high pressure line going to the injector. Then the little piece with the needle at the end is the fuel rack, it swings back and forth and controls the amount of fuel going to the injector.

Here a a view of where the pump sits in the block:



The cast aluminum arm sticking up comes from the governor shaft and goes to the fuel rack. The little ball on the bottom of the fuel rack sits in the governor arm fork.



Finally the pump mount from the top:



It's held on with three 1/4" studs and nuts, and the shim(s) underneath is added at the factory to get the injector timing right. I believe is you remove a shim it will advance the injector timing.

Anyways, I think I'll take the head apart next and get a look at the valves, rockers, ect.

very nice tear-down, that is crazy on the damaged that is caused.

Cool motor, on how it works. Any way that cast iron piston rod can fit into a gas motor? Be cool if it can since a cast iron rod is better then an aluminum rod?

SteamNut247 wrote:

very nice tear-down, that is crazy on the damaged that is caused.

Thanks. Yeah, it sure wild!

prancstaman wrote:

Cool motor, on how it works. Any way that cast iron piston rod can fit into a gas motor? Be cool if it can since a cast iron rod is better then an aluminum rod?

We must be the same level of crazy, becuase I've been thinking about trying that as well! LOL

I was gonna do some measuring of a K Series rod journal and wrist pin, and see how close we are first. Pretty slim chances it will fit without any maching, but it'd still be cool to try!

Break that skirt the rest of the way off with a cold chisel and run it lol. Reduced drag short skirt piston just like that.

Despite being china juenk, that engine sure does look dead simple. Might not be as bad as i thought they were.

RichieRichOverdrive wrote:

Break that skirt the rest of the way off with a cold chisel and run it lol. Reduced drag short skirt piston just like that.

Despite being china juenk, that engine sure does look dead simple. Might not be as bad as i thought they were.

you can do that but if you look at the crack it actually goes through the piston wrist pin also, so if you do that there would be no place to hold the piston on to the connecting rod, so the engine would not run period.